The mass dependence of dark matter halo alignments with large-scale structure

Abstract

Tidal gravitational forces can modify the shape of galaxies and clusters of galaxies, thus correlating their orientation with the surrounding matter density field. We study the dependence of this phenomenon, known as intrinsic alignment (IA), on the mass of the dark matter haloes that host these bright structures, analysing the Millennium and Millennium-XXL $N$-body simulations. We closely follow the observational approach, measuring the halo position-halo shape alignment and subsequently dividing out the dependence on halo bias. We derive a theoretical scaling of the IA amplitude with mass in a dark matter universe, and predict a power-law with slope ${\beta }_{\mathrm{M}}$ in the range $1/3$ to $1/2$, depending on mass scale. We find that the simulation data agree with each other and with the theoretical prediction remarkably well over three orders of magnitude in mass, with the joint analysis yielding an estimate of ${\beta }_{\mathrm{M}}=0.36_{-0.01}^{+0.01}$. This result does not depend on redshift or on the details of the halo shape measurement. The analysis is repeated on observational data, obtaining a significantly higher value, ${\beta }_{\mathrm{M}}=0.56_{-0.05}^{+0.05}$. There are also small but significant deviations from our simple model in the simulation signals at both the high- and low-mass end. We discuss possible reasons for these discrepancies, and argue that they can be attributed to physical processes not captured in the model or in the dark matter-only simulations.

12 pages, 6 figures; accepted for publication in MNRAS

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• KiDS-1000: Constraints on the intrinsic alignment of luminous red galaxies
• The MillenniumTNG Project: Intrinsic alignments of galaxies and halos
• On the Cosmic Web Elongation in Fuzzy Dark Matter Cosmologies: Effects on Density Profiles, Shapes and Alignments of Halos
• Modeling Intrinsic Galaxy Alignment in the MICE Simulation
• Delensing the CMB with the cosmic infrared background: the impact of foregrounds
• The impact of Self-Interacting Dark Matter on the Intrinsic Alignments of Galaxies
• Analysis method for 3D power spectrum of projected tensor field with fast estimator and window convolution modelling: an application to intrinsic alignments
• Three-point intrinsic alignments of dark matter halos in the IllustrisTNG simulation
• KiDS-1000: Weak lensing and intrinsic alignment around luminous red galaxies
• Cosmological evolution of orientations of cluster-sized dark matter haloes and their central galaxies in the Horizon-AGN simulation
• Tightening weak lensing constraints on the ellipticity of galaxy-scale dark matter haloes
• Galaxy clusters as intrinsic alignment tracers: present and future
• A rising tide: Intrinsic alignments since the turn of the millennium
• B-modes from galaxy cluster alignments in future surveys
• Intrinsic and extrinsic gravitational flexions
• The AIDA-TNG project: 3D halo shapes
• Etherington duality breaking: gravitational lensing in non-metric spacetimes versus intrinsic alignments
• Realistic systematic biases induced by residual intrinsic alignments in cosmic shear surveys